When we look at mitochondrial DNA variation and we trace it back to a single common ancestor that it traces back to a single woman. And this is the, for better or for worse, it's become known as mitochondrial Eve. And the source of confusion comes about because people then automatically start to think in terms of Eve in the biblical sense and that everyone is derived from a single woman. And it's not that everyone is derived from a single woman, it's that all of our mitochondrial DNAs are derived from a single woman. The reason they are derived from a single woman is because all of life on this planet has a single common origin and is related to that single common origin by a process of descent. And that's also true for our DNA sequence, so that's true for any DNA sequence that one looks at, it isn't, not just mitochondrial DNA. But the fact that mitochondrial DNA is strictly maternally inherited so you got it from your mother who got it from her mother from her mother from her mother and so forth, means that as we go back through this process of descent tracing back to a single common origin to a single common ancestor that has to be a single woman who was living at some point in the past somewhere. That doesn't mean that woman didn't have other, was not a member of a population, she most certainly was; she had contemporaries, they had mitochondrial DNAs, they left descendants. But it's just by chance, some point in their line of descent, either they had no daughters or, either no offspring or no daughters. But either way their mitochondrial DNA types went extinct. Until eventually all the mitochondrial DNA types we see today only trace back to a single individual in that ancestral population.